The present invention relates generally to techniques for storage replication, and in particular to techniques for remote storage replication.
Conventionally, there have been two types of approaches to storage-based replication, local and remote replication. Both technologies mirror files, filesystems, or volumes without using host CPU power. When a host writes data to a volume containing production data (PVOL), the storage system automatically copies the data to a replication volume (SVOL). This mechanism ensures that PVOL and SVOL are identical.
The local replication approaches duplicate volumes within one storage system, so that the PVOLs and SVOLs are in the same storage system. The local replication approaches are typically used for taking backups. When a user by manual means, or a back-up program, splits a mirrored pair, data written from a host is no longer copied to the SVOL. Accordingly, the SVOL now contains a backup of PVOL. To restore the whole volume, the user can re-synchronize PVOL with SVOL. To restore individual files, the user can copy files from SVOL to PVOL through host.
The remote replication duplicates volumes across two or more storage systems. Data is transferred through paths, such as ESCON, Fibre Channel, T3, and/or IP networks, directly connecting two storage systems. The remote replication typically used to recover data from disasters, such as earthquake, flood, fire, and the like. Even if the storage system or the whole data center at the primary site is damaged by a disaster, data is still at the secondary site and businesses can be resumed quickly.
While certain advantages are perceived, opportunities for further improvement exist. For example, according to conventional replication approaches, information must be sent to each SVOL from each PVOL along a particular path. When the path is a high bandwidth path, usage charges can mount. On the other hand, if the path is not of sufficient bandwidth, the copy operations can lag behind.
What is needed are improved techniques for managing storage based replication.